8 SEPTEMBER 2017 • FOGHORN FOGHORNFOCUS: TECHNOLOGY was made to reduce service speed, a highly effective way to reduce fuel consumption. Emphasis was placed on mini- mizing time spent at berth in order to maintain the existing timetable, despite the reduced service speed. Passenger transfer rates were increased, largely due to the single accom- modation deck layout with double access doors. The flow of travelers was improved through careful design of seating arrangements, walkway arrangements, and luggage storage areas, and supported by additional features that include a dedicated storage area for bicycles and an external seating area. For future catamaran designs, computational analysis to model the flow of individual passengers is a key capabil- ity that will enable further design optimization in this aspect of design. Wightlink reported that since entering service, Wight Ryder I and Wight Ryder II have reduced fuel consumption on the route by 48 percent compared to the same period of operation for the previous ferry fleet, based on an identical service schedule. This is not only because of reduced time spent in berth, but also because of the fully-optimized catamaran hull form, highly-efficient propulsion system technology using advanced electronic management systems, lightweight construction materials, and specialist hull coatings. The Wightlink catamarans are a prime example of how state-of-the-art catamaran technology coupled with the right layout can help vessel operators reduce the environ- mental impact of business operations and make significant cost savings. Following the success of the Wightlink project, we ran comparisons of fuel consumption for the Wightlink cata- marans against a comparable monohull ferry with the same service speed and deadweight capability. At 25 knots, the catamaran demonstrates 12 percent fuel savings over the monohull, just going to show that two hulls are better than one! Case Study #3 – Designing for rough water routes Physical model testing has always played an important role in the development and optimization of new ferry designs, particularly to confirm vessel motions and to predict motion sickness incidence (MSI) among passengers in waves. However, these tests are very often time-consuming and expensive. As with CFD, numerical seakeeping simulations can provide an accurate and cost-efficient way to obtain good data for vessel motions in lieu of physical model tests, allowing quick assessments to be made for the effects of hull form geometry changes or ride control systems, for example. For the last decade, BMT has been using numerical seakeep- ing software extensively in the development of innovative catamaran designs for the U.S. Navy and commercial vessel operators. In 2001, BMT Nigel Gee undertook a research and de- velopment project sponsored by the Navy’s Office of Naval Research (ONR) to develop a catamaran hull form that offers significantly improved seakeeping performance with minimal calm water resistance penalty. The advanced semi- SWATH hullform, denoted ‘ModCat’, adopted narrower sections at the waterline, with a lower center of buoyancy and a slender bulb at the bow. In comparison to a conven- tional catamaran hull form with identical principal partic- ulars, physical model tests demonstrated that the vertical accelerations of the ModCat were up to 50% lower than those of the conventional catamaran, with only a 5% increase in power required to achieve the same speed. The ModCat hull form has subsequently been adopted for military applications in the Atlantic Ocean (260-ft/55 knot U.S. Navy Sea Fighter) and for rough water ferry op- erations in the Pacific Ocean (187-ft/33 knot passenger and vehicle ferry, Betico II). In 2010, BMT designed a more extreme variant of the Modcat hullform when U.K.-based operator Turbine Transfers challenged us to develop the next generation of wind farm support catamarans. The operator wanted a vessel with excellent seakeeping capabilities to allow comfortable transfers to offshore wind turbines. Small Waterplane Area Twin Hull (SWATH) vessels demonstrate by far the best sea- keeping performance in large waves, but at the expense of Wightlink Catamarans Betico II Rough Water Ferry